A basic principle of a Transparent Interconnection of Lots of Links (TRILL) is, by applying an extended Intermediate System to Intermediate System (ISIS) link state protocol to a data link layer network, that is, a layer 2 network, a problem of low utilization of link bandwidth and a small networking scale in a Spanning Tree Protocol (STP) technology used in the layer 2 network is overcome.
A virtual private local area network service (VPLS) may enable that user networks that are geographically isolated can be connected through a wide area network, so that a connection effect among networks is just like being in a local area network. Therefore, multiple TRILL networks may be interconnected by means of the VPLS. A network formed by means of interconnection through the VPLS is called a TRILL over VPLS network in the following. TRILL over VPLS enlarges a TRILL network, which is beneficial to unified management and maintenance of the multiple TRILL networks.
In TRILL over VPLS, a packet is forwarded using a virtual switch instance (VSI), a correspondence exists between a user virtual local area network (VLAN) and the VSI, and a virtual switch instance identity (VSI ID) corresponding to the user VLAN may be acquired according to the correspondence between the user VLAN and the VSI. When a broadcast, unknown unicast or multicast (BUM) packet enters the VPLS, a VPLS provider edge (PE) sends the packet in a VSI to which the VSI ID belongs, and broadcasts, to all PEs through a PW port, the BUM packet accessing the VPLS. Because in a broadcast process, a local VPLS PE does not differentiate a remote PE that needs to receive the BUM packet, but copies the BUM packet and sends the BUM packet to all remote PEs at a local PE pseudo wire (PW) side; for a remote PE that does not need to receive the BUM packet, a waste of bandwidth between the local PE and the remote PE is caused.